Correct sim function, and add set_obs and set_obs_list functions.

The CTA observation container was not copied in the sim function following yesterday's merge, this was corrected.

The set function is now obsolete, and has been renamed to set_obs for clarity. The set function is still there, but a warning is issued if it is still used.

A set_obs_list function has been added that allows setting lists of observations.
Correct for thread safety in ctobssim.

ctobssim was not fully thread save as the models were shared among the threads which led to concurrent memory access when evaluating the Monte Carlo cache. The models are now copied within the parallel section, avoiding concurrent memory access (#1258).
Add pointing pattern definition and observation list definition to obsutils. Enhance cspull so that observation patterns can be simulated.